re: So that was awkward

So I'm in the car with my friend and his girlfriend. Girlfriend is talking about her younger sister and how this will probably be the last year she will believe in Santa Claus, she says her sister is going to be upset when she finds out. So I chime in at that moment, "Well, if she is going to be upset about Santa, just wait until she finds out about God." Car went silent, not my best moment.